package packaging

import (
	"archive/zip"
	"bytes"
	"context"
	"io"
	"os"
	"path/filepath"
	"strings"

	"golang.org/x/xerrors"

	dio "github.com/aquasecurity/go-dep-parser/pkg/io"
	"github.com/aquasecurity/go-dep-parser/pkg/python/packaging"
	"github.com/aquasecurity/trivy/pkg/fanal/analyzer"
	"github.com/aquasecurity/trivy/pkg/fanal/analyzer/language"
	"github.com/aquasecurity/trivy/pkg/fanal/types"
)

func init() {
	analyzer.RegisterAnalyzer(&packagingAnalyzer{})
}

const version = 1

var (
	requiredFiles = []string{
		// .egg format
		// https://setuptools.readthedocs.io/en/latest/deprecated/python_eggs.html#eggs-and-their-formats
		".egg", // zip format
		"EGG-INFO/PKG-INFO",

		// .egg-info format: .egg-info can be a file or directory
		// https://setuptools.readthedocs.io/en/latest/deprecated/python_eggs.html#eggs-and-their-formats
		".egg-info",
		".egg-info/PKG-INFO",

		// wheel
		".dist-info/METADATA",
	}
)

type packagingAnalyzer struct{}

// Analyze analyzes egg and wheel files.
func (a packagingAnalyzer) Analyze(_ context.Context, input analyzer.AnalysisInput) (*analyzer.AnalysisResult, error) {
	r := input.Content

	// .egg file is zip format and PKG-INFO needs to be extracted from the zip file.
	if strings.HasSuffix(input.FilePath, ".egg") {
		pkginfoInZip, err := a.analyzeEggZip(input.Content, input.Info.Size())
		if err != nil {
			return nil, xerrors.Errorf("egg analysis error: %w", err)
		}

		// Egg archive may not contain required files, then we will get nil. Skip this archives
		if pkginfoInZip == nil {
			return nil, nil
		}

		r = pkginfoInZip
	}

	p := packaging.NewParser()
	libs, deps, err := p.Parse(r)
	if err != nil {
		return nil, xerrors.Errorf("unable to parse %s: %w", input.FilePath, err)
	}

	return language.ToAnalysisResult(types.PythonPkg, input.FilePath, input.FilePath, libs, deps), nil
}

func (a packagingAnalyzer) analyzeEggZip(r io.ReaderAt, size int64) (dio.ReadSeekerAt, error) {
	zr, err := zip.NewReader(r, size)
	if err != nil {
		return nil, xerrors.Errorf("zip reader error: %w", err)
	}

	for _, file := range zr.File {
		if !a.Required(file.Name, nil) {
			continue
		}

		return a.open(file)
	}

	return nil, nil
}

func (a packagingAnalyzer) open(file *zip.File) (dio.ReadSeekerAt, error) {
	f, err := file.Open()
	if err != nil {
		return nil, err
	}
	defer f.Close()

	b, err := io.ReadAll(f)
	if err != nil {
		return nil, xerrors.Errorf("file %s open error: %w", file.Name, err)
	}

	return bytes.NewReader(b), nil
}

func (a packagingAnalyzer) Required(filePath string, _ os.FileInfo) bool {
	// For Windows
	filePath = filepath.ToSlash(filePath)

	for _, r := range requiredFiles {
		if strings.HasSuffix(filePath, r) {
			return true
		}
	}
	return false
}

func (a packagingAnalyzer) Type() analyzer.Type {
	return analyzer.TypePythonPkg
}

func (a packagingAnalyzer) Version() int {
	return version
}